Essential oil solid compositions

ABSTRACT

Solid composition including a gum material and an tea tree oil and optionally another essential oil wherein the solid composition releases vapor containing the essential oil when exposed to an effective flow of gas. A method of diffusing tea tree oil into the atmosphere and a method of disinfecting air conditioning systems are also provided.

FIELD OF THE INVENTION

The present invention relates to solid compositions which release avapour containing at least one essential oil when exposed to effectiveair flow. The present invention also relates to methods of producing thesolid compositions; and to methods of disinfecting air conditioningsystems using the solid compositions.

BACKGROUND OF THE INVENTION

Tea tree oil is a natural essential oil from a tree of the classMyrtenceae, especially of Melaleuca. Tea tree oil has been used as abroad spectrum topical antiseptic for more than 70 years. In recenttimes, the anecdotal evidence as to the antimicrobial efficacy of teatree oils has been substantiated by scientific evidence. Such evidencecan be found in the work of Carson, C. F. and Riley, T. V, Antimicrobialactivity of the Major Components of the essential oil of MelaleucaAlternifolia, Journal Applied Bacteriology, 78, 264-269 (1995); C. F.Carson, B. D. Cookson, H. D. Farrelly and T. V Riley, Susceptibility ofmethicillin-resistant Staphylococcus aureaus to the essential oil ofMelaleuca Alternifolia, Journal Antimicrobial Chemotherapy, 35, 421-424(1995); and Carson, C. F., Hammer, K. A. and Reiley, T. V. (1996) Invitro activity of the essential oil of Melaleuca Alternifolia againstStreptococcus spp. Journal of Antimicrobial Chemotherapy 37: 1177-1178.

It is well recognised that commercial, industrial and hospital airconditioning ducting can be a major source of infection and re-infectionin public and private buildings. The World Health Organisation (WHO)reported its findings on this subject in 1988. This report in briefstated that biological air contaminants in indoor air have beenassociated with half of all absenteeism and reduced worker efficiencydiscovered in the report.

International publication No. WO 88/10122 (Commonwealth Industrial GasesLtd) describes the use of a biocidal composition comprising an oil ofMelaleuca in disinfecting air conditioning systems. This procedureinvolves solubilising the tea tree oil in both ethanol and carbondioxide and delivering the solubilised tea tree oil by gaseous carbondioxide into air conditioning ducting. The procedure therefore requiresa constant supply of carbon dioxide by way of carbon dioxide gascylinders. Specialised equipment such as a high pressure rated gun,hoses and other automatic delivery apparatus are also required. Inaddition to the fact that this procedure requires specialised equipmentand highly trained personal, the possible hazards associated with theuse of carbon dioxide in these procedures are well documented. A saferand more cost effective procedure for disinfecting air conditioningsystems is therefore desirable.

The positive effects of dispersing pleasant aromatic essential oilodours into public building air space are now well described in themedical literature. The traditional manner for achieving this is by theuse of either electric diffusers or by candle warmed water or oildispersed essential oil burners.

At the Plane Tree Public Hospital in California patients are given achoice of fragrances. In the St Croix Valley Memorial Hospital,Wisconsin, natural fragrances are used to counteract unpleasant odoursand to generally improve the atmosphere of all patient care and amenityrooms. The Sloane Kettering Institute in New York has reported that theuse of Heliotropin, a vanilla like perfume, has significantly reducedstress in cancer patients. Lavender and Camomile essential oils are nowin regular use in hospitals in the United Kingdom. Where elderlypatients have demonstrated a tendency to insomnia the use of lavenderhas been found to lead to less restlessness and an actual increase inthe number of hours sleep.

At the Japan School of Medicine the worker Sagano has reported that theuse of natural fragrance will help both in the relaxation of staff andpatients. International Airlines as Virgin Airlines and New ZealandAirlines are using pure essential oils to assist customers overcometravel fatigue and jet lag. International Hotel Groups as the MarriottChain use essential oil odours in the lobby areas of many of theirhotels.

In all of the examples cited above traditional methods of dispersing thenatural essential oil odours are employed. It is desirable to develop amethod of dispersing essential oils which eliminates the need forelectrical or candle or other such diffusers.

SUMMARY OF THE INVENTION

The present inventors have now developed a solid composition whichreleases microscopic essential oil vapour when exposed to an effectiveflow of gas such as that generated by an air conditioning system. Whenplaced in air conditioning ducts, solid compositions of the presentinvention release an essential oil vapour. In cases where the essentialoil used in the solid composition exhibits antimicrobial activity, suchas tea tree oil, the solid compositions release a germicidal oil vapour.These compositions therefore provide a relatively safe and inexpensivemeans for dispersing essential oils in a given environment or fordisinfecting air conditioning systems.

Accordingly, in a first aspect the present invention provides a solidcomposition including a gum material and tea tree oil wherein the solidcomposition releases vapour containing the tea tree oil when exposed toan effective flow of gas.

The gum material may be any material classified as a gum or hydrocolloidincluding proteins, polysaccharides (for example, microbialpolysaccharide exudates), carbohydrates and celluloses or mixturesthereof.

In a preferred embodiment, the gum material includes carrageenansextracted from red seaweeds. Rhodophyeae-Gigartinales, familiesGigartinaceae and Solieriaceae and example species Eucheuma coltinii,Chondrus crispus, Eucheuma spinosan and Gigarta stellata are suitablered seaweeds for a source of primary gum materials.

In a further preferred embodiment the carrageenans include kappa, iotaor lambda fractions or mixtures thereof.

In another preferred embodiment the gum material includes agalactomannan. Preferably, the galactomannan has a molecular weight ofapproximately 300.000 and is non-ionic. The galactomannan may be locustbean gum derived from the legume Ceratonia siliqua.

In another preferred embodiment the gum material includes a microbialexudate. The exudate may be derived from a bacterium such as Xanthomonascampestris. The microbial exudate may be Xanthan gum.

In a more preferred embodiment the gum material includes a mixture oftwo or more materials selected from carageenans, locust bean gum andXanthan gum.

Preferably, the gum material is present in the solid composition at aconcentration of between 2 and 10 wt %, more preferably between 3 and 6wt %.

In a further preferred embodiment deionised water is used to prepare thegum material solution. Preferably, the pH of a 1% solution of the gummaterial solution is in the range of 7 to 9.

The term "essential oil" when used herein encompasses both syntheticessential oils and naturally occurring essential oils. Non-limitingexamples of essential oils are oils of various fruits such as apple,cherry, pineapple and the like, oils of various woods such as cedar,pine, briar and the like, oils of various flowers or herbs such asruses, violets, tobacco flowers and the like, and other such fragrancessuch as peppermint, menthol, camphor, methyl salicylate, eucalyptus,parachlor benzene, acetates and in general essential oils such asalcohols, aldehydes, esters, terpenes, tars, phenols, thaymols and thelike.

In one preferred embodiment the essential oil exhibits antimicrobialactivity. Non-limiting examples of oils which exhibit antimicrobialactivity include oils obtained from tea trees, thyme, lemongrass,lemons, oranges, anise, clove, roses, lavendar, citronella, eucalyptus,pepermint, camphor, sandalwood and cedar and combinations thereof.

In a preferred embodiment the essential oil is an aromatic oil or a teatree oil or a mixture thereof.

The aromatic oil may be selected from one or more of the groupconsisting of heliotropin, lavender, camomile, a lemon scented oil (suchas the oil of Leptospermum liversidgeii), sandalwood and jasmine.

The essential oil of the species Leptospermum liversidgeii has a uniqueand long lasting natural lemon odour. The present inventors have foundthat compared to other lemon scented species (notably Leptospermumpetersoni) this species delivers the most pleasant of lemon odours anddoes so for the longest duration.

In a further preferred embodiment, the solid composition also includes afixative. By "fixative" we mean a component which prolongs theevaporation rate of an aromatic oil.

The fixative may be selected from the group consisting of musk ketone,coumarin, eugenol and vanillin. The natural hydrocarbon componenteugenol is a preferred fixative for fragrant materials.

In the oil of Leptospermum liversidgei, eugenol is present in relativelyhigh amounts. This factor combined with the other constituents such ascitronellal, alpha pinene, linalool and thymol work together to producenaturally a long lasting pleasant lemon aroma. The present inventorshave found that by combining the natural fixative elements present inthe oil of Leptospermum liversidei, unique and pleasant long lastingaromatic blends containing lavender or camomile can be produced. Thefinished aroma can have a lemon scent or it can display the fragrance oflavender or camomile. These examples are non-limiting and anycombination of fragrances that can be incorporated into solid gumcompositions are encompassed by the present invention.

Preferably, the essential oil is present in the solid composition at aconcentration of between 5 and 20% v/v, more preferably between 10 and15% v/v.

The essential oil may be solubilised by any known means such as byadmixture with an alcohol or a surfactant or a mixture thereof. Thealcohol may be ethanol, propan-2-ol (isopropyl alcohol), propyleneglycol or methanol.

In a preferred embodiment, the essential oil is solubilised by admixturewith a non-ionic surfactant which allows a low weight surfactant toweight of tea tree oil composition. Preferably, the surfactant is analcohol ethoxylate. In a more preferred embodiment, the alcoholethoxylate is polyoxyethylene (2) oleyl ether.

In a second aspect the present invention provides a method ofsolubilising an essential oil which includes

i) heating a predetermined amount of an alcohol ethoxylate to atemperature of between 25° C.-45° C.; and

ii) adding a predetermined amount of the essential oil to the heatedalcohol ethoxylate.

The preferred method of solubilising essential oil provided by thepresent invention is advantageous in that it results in an essential oilsolution wherein the weight to weight ratio of surfactant to tea treeoil is relatively low. Weight to weight ratios of less than 1 to 1 canbe achieved by following the solubilisation method of the presentinvention.

The low weight to weight surfactant to essential oil solutions arepreferable for the following reasons:

i) High weight to weight surfactant to essential oil mixtures often giverise to solutions which are hazy, cloudy or opalescent. These cloudy oropalescent solutions are generally not desirable for commercial reasons.The low weight to weight surfactant to essential oil solutions can bediluted with water to produce bright clear solutions.

ii) A relatively high mass of surfactant can inhibit the broad spectrumgermicidal efficacy of an essential oil such as tea tree oil. The lowerthe weight surfactant the higher the efficacy of natural oil as measuredby standard Minimum Inhibitory Concentration (MICS) analysis.

In a further preferred embodiment of the present invention, the solidcomposition is in the shape of a disc.

In a further preferred embodiment the disc is a flat discus shape with abase surface and a top surface and a side wall connecting the basesurface to the top surface. Preferably, the diameter of the top surfaceis less than the diameter of the base surface.

In a preferred embodiment the ratio of the height of the side wall tothe width (circumference) of the top surface is between 1:10 and 1:11.5.For example, a preferred disc may have a side wall height of 20 mm and atop surface width (circumference) of 230 mm. A disc of the presentinvention may, for example, have the following dimensions:

Base surface: 250 mm

Top surface: 210 mm

Height: 40 mm.

In a further preferred embodiment the side wall is shaped in a camber.Preferably, the angle of connection between the base and top surfaces isequal to or less than 65 degrees and more preferably equal to or lessthan 62 degrees and 57 minutes.

In a further preferred embodiment the solid compositions of the presentinvention have a total weight of between 0.5 and 5 kg. More preferably,the solid compositions have a total weight of between 0.9 and 3 kg.

The preferred dimensions of a disc according to the present inventionprovide an advantage in that a slow and even diffusion of natural oilfrom the disc occurs in the presence of air flow.

In a third aspect the present invention provides a method of preparing asolid composition which method includes

i) dissolving a gum material in an aqueous solution:

ii) heating the gum material solution to a temperature of between 60° C.and 95° C.;

iii) admixing the heated gum material solution with a tea treeoil/surfactant solution; and

iv) placing the admixed solution from step iii) into a mould.

It will be appreciated that the present invention provides a simple andcost-effective means for dispersing essential oils in a givenenvironment. The solid compositions of the present invention can besimply placed in air conditioning ducts by unskilled labour so as todiffuse essential oils into the air stream.

Accordingly, in a fourth aspect the present invention provides a methodof diffusing tea tree oil into the atmosphere which method includesexposing a solid composition including a gum material and the tea treeoil to an air flow such that the solid composition releases vapourcontaining the tea tree oil.

In a preferred embodiment the solid composition is exposed to an airflow by placing the solid composition in an air conditioning duct.

It will be appreciated that the preferred solid compositions of thepresent invention also provide a simple and cost effective means ofdisinfecting air conditioning systems. Unlike systems described in theprior art, the preferred compositions of the present invention do notrely on solubilising the essential oil in alcohol or gaseous carbondioxide. The preferred non toxic water-based gum disc-shapedcompositions allow germicidal oil vapour to diffuse slowly andconstantly in the presence of the air flow generated in air conditioningducting.

Accordingly, in a fourth aspect the present invention provides a methodof disinfecting an air conditioning system which method includes placinga solid composition in a duct of the air conditioning system, the solidcomposition including a gum material and tea tree oil, wherein thecomposition releases antimicrobial vapour containing the tea tree oilwhen exposed to an effective flow of gas.

In a preferred embodiment, the essential oil is tea tree oil.

The term "air conditioning system" as used herein refers collectively toducts, fans, filters, humidifiers, coolers and other plant and equipmentassembled for air conditioning to parts of such systems.

DETAILED DESCRIPTION OF THE INVENTION

In order that the nature of the present invention may be more clearlyunderstood preferred forms thereof fill now be described with referenceto the following Examples.

EXAMPLE 1

Tea Tree Oil Compositions

In a preferred embodiment of the invention the tea tree oil ismanufactured in accordance with the ISO 4730 standard. Preferably, thetea tree oil is a pharmaceutical grade material. Table 1 describes thecharacteristics of an ISO 4730 standard tea tree oil. In a mostpreferred embodiment the tea tree oil conforms with the ISO 4730standard prescribed in Table 1 but with component values in respect to1,8 cineol less than 4% and preferably 2.2-3.0%; and terpinen-4-olvalues greater than 37% and preferably 39-41%. Table 2 shows results ofgas chromatic analysis for two batches of the preferred TEETEEOH! brandpharmaceutical grade tea tree oil.

                                      TABLE 1                                     __________________________________________________________________________    The ISO Standard 4730 prescribes the following physical and component         details for Australian Single Distilled Tea Tree Oil -Oil of Melaleuca        Alternifolia                                                                  Physical                                                                      State      Liquid                                                             __________________________________________________________________________    Colour     Visually colourless to pale yellow                                 Odour      Typically Myristic                                                 Specific   Method ISO 279 20 Degrees C/20 degrees C 0.885-0.906               Gravity                                                                       Refractive Method ISO 280                                                     Index      1.475 to 1.482                                                     Optical    Method ISO 592                                                     Rotation   +5 degrees to +15 degrees                                          Solubility In 85% V/V Ethanol at 20 Degrees C the Miscibility should be                  such that one volume of the oil shall require not more than                   two volumes of 85% ethanol to give a clear solution                           This is tested in accordance with ISO Method 875                   Flash Point                                                                              Penskey Martens Closed Cup IP 34                                              In typical Range 57 degrees C to 60 Degrees C                      Fire Point Cleveland Open Cup IP 36-72 Degrees C.                             Component  There are 15 components determined by gas chromatographic          Range      analysis in accordance with method ISO 7609-1985 which are                    identified as being truly representative of genuine oil of                    melaleuca alternifolia in the TSO 4730 standard. These are                    listed below. The components described as Ledene                              (Viridiflorene), delta-Cadinene, Globulol and Viridiflorol                    are                                                                           each components found only in the prescribed rations in                       genuine oil of melaleuca alternifolia and are said to be                      "genuine marker components for tea tree oil (oil of melaleuca                 alternifolia)."                                                    Component  ISO 4730 Range %                                                   alpha-Pinene                                                                             1-6                                                                Sabinene   Trace-3.5                                                          alpha-Terpinene                                                                          5-13                                                               Limonene   0.5-4                                                              para-Cymene                                                                              0.5-12                                                             1,8 Cineole                                                                              0-15                                                               gamma-Terpinene                                                                          10-28                                                              Terpinolene                                                                              1.5-5                                                              Terpene-4-ol                                                                             30 plus                                                            alpha-Terpineol                                                                          1.5-8                                                              Aromadendrene                                                                            Trace-7                                                            Ledene (Viridiflorene)                                                                   0.5-6.5                                                            delta-Cadiuene                                                                           Trace-8                                                            Globulol   Trace-3                                                            Viridiflorol                                                                             Trace-1.5                                                          __________________________________________________________________________

                  TABLE 2                                                         ______________________________________                                        Teeteeohl Brand Pharmaceutical Single Distilled Australian Tea Tree Oil       (Oil of Melaleuca Alternifolia)                                                                          ISO 4730                                           COMPONENT      VALUE %     STANDARD %                                         ______________________________________                                        Batch Number 1029                                                             alpha-Pinene   0.7         1-6                                                Sabinene       0.5         Trace-3.5                                          alpha-Terpinene                                                                              9.7         5-13                                               Limonene       1.0         0.5-4                                              para-Cymene    2.7         0.5-12                                             1,8 Cineole    2.8         0-15                                               gamma-Terpinene                                                                              20.9        10-28                                              Terpinolene    3.4         1.5-5                                              Terpinen-4-ol  40.0        30 plus                                            alpha-Terpineol                                                                              2.5         1.5-8                                              Aromadenedrene 1.3         Trace-7                                            Lendene (Viridiflorene)                                                                      1.1         0.5-6.5                                            delta-cadinene 1.1         Trace-8                                            Globulol       0.4         Trace-3                                            Viridiflorol   0.2         Trace-1.5                                          BATCH 1021                                                                    alpha-Pinene   2.4         1-6                                                Sabinene       0.6         Trace-3.5                                          alpha-Terpinene                                                                              10.1        5-13                                               Limonene       1.0         0.5-4                                              para-Cymene    2.3         0.5-12                                             1,8 Cineole    3.0         0-15                                               gamma-Terpinene                                                                              20.8        10-28                                              Terpinolene    3.4         1.5-5                                              Terpinen-4-ol  41.4        30 plus                                            alpha-Terpineol                                                                              2.6         1.5-8                                              Aromadenedrene 1.1         Trace-7                                            Lendene (Viridiflorene)                                                                      0.9         0.5-6.5                                            delta-cadinene 0.9         Trace-8                                            Globulol       0.3         Trace-3                                            Viridiflorol   0.2         Trace-1.5                                          ______________________________________                                    

EXAMPLE 2

Tea tree oil solid composition

A carrageenan locust bean gum mixture is selected which has beenstandardised with the addition of appropriate salts and polysaccharidesso the mixture possesses the following characteristics: Viscosity: 400to 600 centipoises measured as a 2.5% aqueous solution on a Brook fieldRVT Viscometer, operating at 20 revolutions per minute and with solutionheated to 70 degrees centigrade.

The pH of the Carrageenan, locust bean gum mixture is in the range 7-9%when a 1% solution of the mixture is measured.

The particle size of the combined dried mixture is such that more than98% is finer than 250 microns. The total moisture content of the mixtureis not greater than 14%. The gel strength of the mixture is between 1800and 2200 measured in a Kobe tester a solution strength of 2.5%. Thecarrageenans are a mixture of kappa and iota component containing types.

The water for first dispersing the carrageenan and locust bean gummixture and then heating to gelatinisation is de-ionised water.

The carrageenan locust bean gum mixture is first wetted to aiddispersion with ethanol. A mixture of pure tea tree oil and surfactantis made. The tea tree oil is as described above and conforms with ISO4730. The actual tea tree oil used is TEETEEOH! Brand Australian SingleDistilled Pharmaceutical Grade with the following important componentvalues; the 1, 8 cineole is in the range 2.2-2.5% and the Terpinene-4-olin the range 39-41%.

The surfactant used is polyoxyethylene (2) oleyl ether. The surfactantis measured so that sufficient is available to solubilise the tea treeoil. The measured surfactant is heated approximately 37 degree C. Thecarefully measured tea tree oil is poured into the heated surfactant andstilled vigorously. The finished solution is bright and clear.Sufficient de-ionised water is added to the surfactant-tea tree oilmixture as is required. This bright clear mixture is set aside.

The wetted carrageenan-locust bean gum mixture described above is mixedwith sufficient cold water. The water temperature is no greater than 12degrees C. The well dispersed carrageenan-locust bean gum mixture isgradually heated with vigorous stirring to 90 degrees C. The mixture isheld at 90 degrees C. for several minutes. The mixture is allowed tocool to 70 Degrees C. To the cooled carrageenan-locust bean gum mixtureis added the tea tree oil-surfactant solution. This has the immediateeffect of rapidly cooling the mixed solution further. The cool mixtureis poured carefully into rubber moulds. The moulds are formed so thatthe finished gel has a distinctive flat discus shape as describedpreviously. The surface area of the top of the discus shape ispreferably less than the surface area of the bottom of the discus shape.The ratio of the height (side wall) of the discus to its surface ispreferably of the order of 1:10 or 1:11.5 but this ratio is notessential. The edge of the discus shape is preferably carefully shapedso as to provide a gradual camber. This is preferable so that even airdiffusion takes place with the finished Tea Tree Gel Disc. The mixturecan be de-moulded with 30 minutes. The Tea Tree Gel-Discs so formed areallowed to cool completely.

Upon complete cooling the discs may be packed in suitable plastic andfurther packed in recyclable cardboard cartons. The plastic may bepolyethylene-plastics does type 4, polypropylene-plastics code type 5,or preferably Fluorinated--High density Polyethylene-plastics code type2-modified. No colouring matter is used in the manufacture of any typeof Tea Tree Gel-Disc. The final Tea Tree Gel Disc in this examplecontains 10% tea tree oil. The Tea Tree Gel Disc in this example has ashelf life of 12 months wrapped and packaged. The tea Tree Gel Disc inthis example has an unwrapped normal room air circulation life ofbetween 30 and 45 days.

When installed into an air conditioning ducting this Tea Tree Gel Discmay have a life of between 7 and 10 days. The Gel Disc life in an airconditioning system is dependent on the systems air flow and airtemperature. The tea tree gel disc manufactured in accordance with thismethod can be described as having low to very low syneresis.

EXAMPLE 3

Tea tree oil solid composition

A carrageenan locust bean and xanthan gum mixture is selected which hasbeen standardised with the correct addition of salts and saccharides.The carrageenan has a viscosity of 400 to 600 centipoises as measured ina 2.5% solution on a Brookfield RVT viscometer at 20 revolutions perminute and solution heated to 70 degrees C. The pH of the carrageenan ina 1% solution is between 7 and 9. The total moisture of the powder is14%. The carrageenan tests to a gel strength of 1800 to 2200 in a Kobetest measured at 2.5% in de-ionised water. The carrageenan selected is amixture of carrageenans containing kappa and iota componentcarrageenans. This mixture is dry mixed with a selected xanthan gum. Thedry blended mixture is carefully weighed. To this weighed mixture isadded sufficient ethanol to aid dispersion in cold de-ionised water. Themixture is slowly dispersed in di-ionised water with a commencementtemperature of 12 degrees C. The water is added so that the final gelmixture contains 3.8% selected hydrocolloids. The mixture is graduallyheated to 90 degrees C. under constant stirring. The heated mixture isheld at 90 degrees C. under constant stirring for several minutes. Tothis mixture is added pre-prepared tea tree oil--surfactant solution ofsufficient strength so that the final gel-disc contains no less than 10%v/v tea tree oil. The Tea Tree Oil in Pharmaceutical Standard Materialconforming with ISO 4730.

The tea tree oil surfactant mixture is added to the hydrocolloidsolution which has been cooled to 70 degrees C. The mixture is carefullystirred and allowed to cool further. It is then poured carefully intorubber moulds designed in accordance with disc specifications previouslydescribed. The moulds are released within 30 minutes. The gel discs areallowed to cool. Once cooled the Tea Tree Gel Discs may be packed insuitable plastic film and packed in recyclable fibreboard.

The Tea Tree Gel Discs manufactured in accordance with the method mayhave an air conditioning air diffusion life of between 7 and 10 days.The Gel Discs so produced are bright, shiny and almost transparent. Nocolouring material is used. The tea tree gel disc is manufactured inthis manner can be described as having low syneresis.

EXAMPLE 4

Tea tree oil solid composition

In this example only pure kappa component type carrageenan from thefamily Solieriaceae species Eucheuma cottonii is used. Further, theethanol alcohol which is used to aid dispersion of the carrageenan isalso co-used to solubilise the pharmaceutical grade tea tree oil. Nosurfactants are used in this example. To the carrageenan as selected isadded dextrose monohydrate and maltodexterin with a dextrose equivalentof between 17 and 21. The dry powder is carefully wetted with aproportion of the ethanol and mixed. To this wetted mixture is addedcold water with a temperature of 12 degree C. The mixture is heated to85 degrees C. and held for exactly 2 minutes. This solution is cooled to70 degrees C. To the cooled mixture is added a pre mixed solution ofethanol and pharmaceutical grade tea tree oil. The tea tree oil conformswith ISO 4730 standard. The mixture is stirred vigorously. The rapidlycooling mixture is poured into suitable rubber mould prepared inaccordance with the disc specification described previously. Within 15minutes the moulds are released and the Tea Tree Gel Discs removed. TheTea Tree Gel Discs are allowed to cool completely. They may be packed insuitable plastic film as described previously. The plastic wrapped teatree gel discs may be packaged in recyclable fibreboard boxes. The teatree gel discs manufactured in this manner are preferably bright andclear and have reasonably hard finished surface. The tea tree gel discmade in the manner in this example have a tea tree oil content of 15%.The solid hydrocolloid matter is 4.8% and the weight of the finished teatree gel discs is 900 grams. The air diffusion life in standard airconditioning ducting for this example was between 7 and 10 days. Thesediscs can be described as having low to very low syneresis.

EXAMPLE 5

Tea tree oil solid composition

Pure kappa component carrageenan derived from Eucheuma cottonnii wasused in this example. No additional salts or saccharides were used. Theweighted carrageenan was wetted only with commercial methylated spirits.The wetted kappa carrageenan was thoroughly mixed and admixed with coldwater at 20 degrees C. The mixture was well dispersed. A pre-preparedmixture of pharmaceutical grade tea tree oil and ethanol was then addedto the cold kappa carrageenan mixture. The proportion of ethanol to teatree oil in the pre-prepared mixture was approximately 2 parts ethanolto 1 part tea tree oil. The complete mixture was stirred vigorously andheated slowly to 85 degrees C. The mixture was kept at 85 degrees C. forapproximatley 45 seconds. By way of a jacketed mixer cold water withtemperature of between 12 and 14 degrees C. was introduced into thejacket as a cooling medium. The mixture was rapidly cooled to below 70degrees C. and poured directly into suitable moulds as previouslydescribed. The moulds were released in 12 minutes. The tea tree geldiscs allowed to cool. The Tea Tree gel discs made in this mannercontained 15% tea tree oil v/v and were carried by a total dryhydrocolloid matter of 5%. The tea tree gel disc were packed aspreviously described. These discs were found to have an air conditioningdiffusion life of between 7 and 10 days. They can be described as lowsyneresis.

EXAMPLE 6

Tea tree oil solid composition

A dry mixture of selected kappa and iota component carrageenans togetherwith locust bean gum, xanthan gum, dextrose monohydrate, 17 DEmaltodextrin, and cations including Sodium salts, Potassium salts andCalcium salts is carefully prepared. The weight of this mixture is suchthat the weight of mixed hydrocolloid in the final preparation is 3%.This mixture is wetted with ethanol. The mixture is carefully dispersedin cold water of a temperature between 8 and 12 degrees C. The mixtureis mixed in a jacketed vessel with accurately controlled heating andcooling capabilities. The stirred mixture is carefully heated to 86degrees C. and held at this temperature for 2 minutes. To this mixtureis added a surfactant solubilised pharmaceutical grade tea tree oilmixture. The tea tree oil mixture is such that in the finished gel discthe tea tree oil content will be 10% v/v. The tea tree oil surfactantmixture is added when the hydrocolloid solution is at 65 degrees C. Thetotal mixture is stirred carefully so as to minimise formation of airbubbles. The cooling mixture is carefully poured into the rubber mouldsas previously described. Within 30 minutes the mould can be released.The Tea Tree Gel Discs are left to cool for 24 hours prior to packing.The gel discs made in this manner have very low syneresis. After 24hours the tea tree gel discs are packed in selected plastic film. Theplastic film wrapped tea tree gel discs are placed into recyclablefibreboard for storage and shipping. No colouring matter is used and thetea tree gel discs have a pleasant opaque creamy to light brown colour.The Tea Tree Gel Discs made in this way have very low syneresis. Therate of diffusion in standard air conditioning systems may be 7 to 10days depending on air flow and temperature range. The net weight of teatree gel disc made in this manner is 900 grams each. The total volume oftea tree oil dissipated in 168 hours is approximately 90 grams. In thefirst 24 hours 18 grams of tea tree oil is dissipated. This is anapproximate equivalent of 0.75 grams per hour in a typical air flowsituation. This is relatively low yet as per the experimental resultsdescribed herein is highly effective in the disinfecting of airconditioning ducting.

EXAMPLE 7

Tea tree oil and lavender solid composition

A carrageenan locust bean gum mixture is selected which has beenstandardised with the addition of appropriate salts and polysaccharidesso the mixture possesses the following characteristics;

Viscosity; 400 to 600 centipoises measured as a 2.5% aqueous solution ona Brookfield RVT Viscometer, operating at 20 revolutions per minute andwith solution heated to 70 degrees centigrade.

The pH of the Carrageenan locust bean gum mixture is in the range of 7-9when a 1% solution of the mixture is measured.

The particle size of the combined dried mixture is preferably such thatmore than 98% is finer than 250 microns, the total moisture content ofthe mixture is preferably less than 14%. The gel strength of the mixtureis between 1800 and 2200 measured in a Kobe tester at solution strengthof 2.5%. The carrageenans are a mixture of kappa and iota componentcontaining types.

The carrageenan locust bean gum mixture is first wetted to aiddispersion with ethanol. A mixture of pure tea tree oil, oil ofLeptospermum Liversidgeii, oil of Lavendula angustifolia (lavender) andsurfactant is made. The tea tree oil is as already described andconforms with ISO 4730. The additional oils are pure as defined by theAustralian Standards.

The surfactant used is polyoxyethylene (20) oleyl ether. The surfactantis measured so that sufficient is available to solubilise all theessential oils described.

The measured surfactant is heated to 37 degrees C. The measuredessential oils are poured into the heated surfactant and stirredvigorously. The finished solution is preferably bright and clear.Sufficient water is added to the surfactant--essential oil mixture asrequired. This bright highly fragrant mixture is set aside.

The wetted carrageenan--locust bean gum mixture described above is mixedwith sufficient cold water. The water temperature is no greater than 12degrees C. The well dispersed carrageenan-locust bean gum mixture isgradually heated with vigorous stirring to 90 degrees C. and held atthis temperature for several minutes. The mixture is allowed to cool to70 degrees C. To the cooled carrageenan-locust bean gum mixture is addedthe essential oil--surfactant solution. This has the immediate effect ofrapidly cooling the mixed solution further.

The cooled mixture is poured into suitable moulds. The cooled discs arepacked in such a way as to have a shelf life of 12 months wrapped.Unwrapped discs have been found to have an operational air conditioningducting lift up to 30 days.

When installed into an air conditioning ducting the discs release apleasant lavender fragrance.

EXAMPLE 8

Fragrant tea tree oil solid composition

In this example, custom made and chosen fragrant essential oil blendsare selected, so that when incorporated with polysaccharides aspreviously described, the fragrance will diffuse into air conditioningducting. Firstly, the fragrant essential oils are selected and blendedso that the chosen fragrance is the most powerful of all fragrancespresent in the mixture. This blend of essential oils is then solubilisedin a selected volume of polyoxyethylene (20) oleyl ether. This mixtureis then added to a pre-prepared complex polysaccharide mixture which maycomprise both kappa and iota type carrageenans and locust bean gum andguar gum.

In this example the most dominant fragrance is that of German Camomileessential oil derived from the species Matricaria recutica.

The method of preparation is similar to other examples described herein.

EXAMPLE 9

Tea tree oil and sandalwood solid composition

In this example and by way of demonstration that a single essential oilfragrant note could be achieved, by combining only one other essentialoil with the oil of Melaleuca alternifolia (tea tree oil) as previouslydescribed. In this example only the oil of Santalum album (sandalwood)was added to that of the tea tree oil.

Whilst maintaining the broad spectrum antimicrobial characteristics oftea tree oil this example shows that the highly aromatic and myrsiticodour of tea tree oil can be simply masked and overpowered by anessential oil such as sandalwood. This is surprising given thatsandalwood is described generally in essential oil and perfumeryliterature as the base note essential oil having an evaporation rate of100 according to the index ascribed to Poucher. This index asserts thatan oil with a maximum score of 100 has the slowest evaporation rate. Byway of comparison, an oil such as lavender which is given an indexnumber of 4, is considered to be a top note essential oil.

The sandalwood tea tree oil mixture is combined with a sufficient amountof polyoxyethylene (20) oleyl ether for solubilisation and the mixtureadded to a cooled mixture of complex polysaccharides. The combined mixis then poured into a suitable mould to form a disc shape as previouslydescribed.

The unwrapped discs so produced can deliver a pleasant fragrance wheninstalled into air conditioning ducting. In circumstances where the airconditioning fans are operating (not necessarily the refrigeration) thesandalwood--tea tree oil solid composition discs may last for up to 30day.

EXAMPLE 10

Summary of test results from trials conducted in air conditioningsystems in a hospital in New South Wales, Australia

The experimental parameters for establishing the broad spectrumgermicidal efficacy of the air diffused water gel tea tree oil solidcompositions is described below;

An air conditioning ducting system was chosen in a major New South WalesAustralia Public Hospital.

This system operated on refrigerated air and the the refrigerant was ofa non CFC type. The air flow was variable to suit and was measuredtypically as cubic metres per minute.

The temperature range of the air flow was measured and automaticallycontrolled so that at ducting inspection points the air temperatureranged between 11 degrees C. and 21 degrees C.

Specially adapted ease of access inspection ports were installed at theselected air conditioning ducting.

Ducting with identical geometry was selected in two separatefloors-nominated as level 3 and level 4.

Only active air diffused water gel blocks containing water miscible teatree oil weer installed on level 3. On level 4 either no gel discs oronly placebo gel discs were installed for control purposes.

Installation was in the manner that two tea tree oil solid compositionswere installed within 600 mm either side of the inspection ducting, sothat one solid composition was up airstream and one down airstream fromthe inspection port.

The solid compositions were placed on the flat floor of each ductingeither side of the inspection port as described above.

The width of the ducting floor was at point 1 level 3 approx 600 mm. Thewidth of the ducting floor at point 2 level 3 was approximately 350 mm.

The ducting floor widths at identical inspection points on level 4 wereapproximately the same as those on level 3.

The air flow into the ducting selected had an airstream which has beenHEPA micro filtered (High Efficiency Particulate Air Filtered).

The ducting systems on both level 3 and level 4 were carefully sampledfor both air and surface microbiological samples as per the accompanyingtable/s.

The sampling was carried out by independent Air Quality Surveyor usingthe most modern air and surface sampling methods and equipment.

The sampling was further supervised by a qualified and practisingmicrobiologist.

The solid compositions were produced by the method described in example2 and were installed on level 3 at 1 inspection point approximately 1hour after this initial sampling.

Further sampling was performed on the same active sites described asinspection points 1 and 2 on level 3 approximately 21 hours later.

Approximately 72 hours after the insertion of the first two solidcompositions, which were only installed at inspection point 1, anadditional four solid compositions were installed on level 3.

Two solid compositions were installed at inspection point 1 on eitherside of the inspection port. Two solid compositions were installed atinspection point 2 level 3 on either side of the inspection port-infloor of the ducting.

The distance between inspection point 1 and 2 is approximately 20metres.

First Microbiological samplings were taken prior to installation of thefirst two solid compositions; further samplings were taken after theinstallation of the additional four solid compositions; installed as twoat each inspection point.

The results obtained from these samplings show clearly themicrobiological efficacy of the solid compositions.

The reduction in Fungal count within the first 21-24 hours wasparticularly significant as fungal contamination of air conditioningducting is of major concern to health and sanitation authorities. Theresults show a greater than 100 fold reduction after 48 hours. In factin the first 21 hour period the fungal reduction was greater than 800fold being reduced from greater than 3200 colony forming units (CFU) toless than 4 CFU.

The rate of diffusion of the solid compositions was as predicted bysmall scale experimental programmes and indicated as 20% within thefirst 24 hours, 20% in second 24 hours, approximately 20% in the third24 hour period. Thereafter the rate of diffusion was at around 10% ineach 24 hour period and reducing so that the total solid composition hadair diffused within the air conditioning ducting by the action of theair flow existing within the system in a period of between 120-168hours.

The results obtained from the trials above are further confirmation ofthe well published efficacy data for tea tree oil which shows theMinimum Inhibitory Concentrations of Australian Tea Tree oil for someorganism as per the table below:

    ______________________________________                                                               MIC %                                                  ______________________________________                                        GRAM POSITIVE BACTERIA                                                        Bacillus cereus          0.3                                                  Bacillus subtilus        0.3-0.4                                              Corynebacterium spp      0.2-0.3                                              Micrococcus luteus       0.2-0.3                                              Propionibacterium acnes  04-0.5                                               Methicillin resistant Staphylococcus                                                                   0.2-0.3                                              aureus                                                                        Staphylococcus epidermis 0.5                                                  Enterococcus faecalis    0.5-0.75                                             GRAM NEGATIVE BACTERIA                                                        Enterobacter aerogenes   0.3                                                  Eschericia coli          0.2                                                  Klebsiella pneumoma      0.3                                                  Proteus vulgaris         0.2-0.3                                              Pseudomonas putida       0.5                                                  Serratia marcescens      0.2-0.3                                              FUNGI AND YEASTS                                                              Aspergillus niger        0.3-0.4                                              Aspergillus flavus       0.4-0.5                                              Candida albicans         0.2                                                  Piryrosporum ovales      0.2                                                  Trychophyton mentagrophytes                                                                            0.3-0.4                                              Trychophyton nibrum      1.0                                                  ______________________________________                                    

EXAMPLE 11

Summary of test results from trials conducted in air conditioning systemin a public hospital in New South Wales, Australia

Sampling performed by Air Quality Services Pty Ltd and Microbiologicalexamination of the samples performed by Biotech Laboratories Pty LtdQueensland.

Test Area

Air conditioning air ducting system. The system comprises straightducting with two in--place inspection points at approximately 25 metresapart.

Air Supply

The system is refrigerated and works on constant supply 24 hours 7 daysper week. The air is HEPA filtered.

Microbiological Sampling

Sampling for airborne bacteria, airborne fungi and mould, surfacebacteria and surface yeast and mould was performed by sterile swab andautomatic air sampling apparatus.

Solid Composition Tea Tree Oil Gel Discs

Solid compositions for this test were produced according to the methoddescribed in Example 2. Two each with a total mass of 2.2 kilograms wereplaced at each inspection point. The water solubilised tea tree oilcontent in each gel disc was 12% v/v.

Sampling Procedure

Samples were taken prior to installing the gel discs. The gel discs wereinstalled either side of the inspection hatch and placed directly on thefloor of the air conditioning ducting.

Bacteria

Both surface and airborne bacteria levels tested were shown to be soinsignificant as unnecessary to be reported in these results.

Surface Yeast and Mould and Airborne Fungi and Mould

These tests indicated very high microbiological contamination.

RESULTS

    __________________________________________________________________________               Date                                                                          05/11/96                                                                             06/11/96                                                                             13/11/96                                                                             19/11/96                                                 SURFACE YEAST AND MOULD CFU/cm                                     LEVEL 3    24 Hour Result       Final Result                                  __________________________________________________________________________    ACCESS POINT 1                                                                           Temp/C 12                                                                            Temp/C 20                                                                            Temp/C 15                                                                            Temp/C 13                                     Against Flow                                                                             44     36     160    20                                            With Flow  8      120    100    8                                             Hatch      >1200  4      <4     <4                                            Hatch      8      <4     <4     <4                                            ACCESS POINT 2                                                                Against Flow                                                                             >1200  <4     12     8                                             With Flow  16     8      8      4                                             Hatch      <4     <4     <4     <4                                            Hatch      <4     16     <4     <4                                            __________________________________________________________________________

AIRBORNE FUNGI AND MOULD CFU/cm

    ______________________________________                                        ACCESS POINT 1                                                                Against Flow   150    50        <50  <50                                      With Flow      100    150       <50  100                                      ACCESS POINT 2                                                                Against Flow   150    50        <50  <50                                      With Flow      <50    200       50   >50                                      ______________________________________                                    

The tea tree oil solid compositions were installed on Nov. 5, 1996(after initial samples taken). These results show significant surfaceyeast and mould at the start of the trial. The 24 hour reduction (asmeasured on Nov. 6, 1996) of the greater than 1200 CFU values indicatethe efficacy of the solid tea tree oil gel discs. The final 14 dayresults further indicate this efficacy.

Airborne Fungi and Mould can be described as insignificant levels. Astatistical reduction is observed.

EXAMPLE 12

Test conditions and results obtained from trials conducted in a majorpublic Bowling Club in Northern New South Wales--Australia.

Sampling performed by Air Quality Services Pty Ltd and Microbiologicalexamination of the samples performed by Biotech Laboratories Pty LtdQueensland.

Test Area

Air conditioning air ducting system/s. The system is a mixed one. Oneair handler supplying quite direct air flow to destination terminals.Another had a split air flow system and ducting constructed with largecurvature in many places.

Sampling was also performed in a public area access site at the pointfurthest from the air handler. This site was at a point in a bistroarea--in the ceiling close to a window. Sampling was also performed at apublic point described as cashier.

Air Supply

The system is refrigerated. The system is idyll for up to 11 hoursdaily. For part of these trials one air handler was re-set so that thefans worked continuously for 24 hours each day for 7 days. Therefrigeration unit was maintained as operational for between 9 and 11hours. The air is filtered prior to entry into the ducting.

Microbiological Sampling

Sampling for airborne bacterium, airborne fungi and mould, surfacebacteria and surface yeast and mould was performed by sterile swab andautomatic air sampling apparatus.

Solid Tea Tree Oil Compositions

In order to fully test the efficacy of the solid composition a number ofcompositions made according to Example 2 were employed.

Sampling Procedure

Samples were taken prior to installing the gel discs. The gel discs wereinstalled either side of the inspection hatch and placed directly on thefloor of the air conditioning ducting.

Bacteria

Surface bacteria valued found are insignificant. Airborne values arehigher--but may be considered also to be unimportant so far as buildinghealth is concerned.

Surface Yeast and Mould and Airborne Fungi and Mould

These are considered high. Species are identified but not described indetail.

Airborne Fungi and Mould

Generally not considered excessive. Results for the public area areindicated for interest.

Temperature and Relative Humidity

Temperatures fluctuated considerably. The relative humidity was high butin line with local atmospheric conditions for the summer period innorthern New South Wales.

RESULTS

TEST SITE A--UPPER CASINO

    ______________________________________                                        YEAST AND MOULD CFU/cm2                                                                    04/02/97                                                                              11/02/97  18/02/97                                       ______________________________________                                        ACCESS POINT 1                                                                Hatch Door     20        <4        4                                          Hatch Door     <4        <4        <4                                         Ducting Floor  640       320       160                                        Ducting Floor  960       640       440                                        ACCESS POINT 2                                                                CASHIER-PUBLIC PLACE                                                          Duct wall - side                                                                             510       240       330                                        Duct wall - rear                                                                             180       200       92                                         ______________________________________                                    

On the start date, Feb. 4, 1997, one composition (10% v/v tea tree oil)was installed after sampling. At the test time Feb. 11, 1997 there wereonly a few grams of the single 10% tea tree oil discs remaining in theducting.

On the Feb. 18, 1997, two further 10 % v/v tea tree oil compositionswere installed. These discs were designed to have slow diffusion rates.

    ______________________________________                                        ACCESS POINT 1   25/02/97 04/03/97                                            ______________________________________                                        Hatch Door       4        8                                                   Hatch Door       <4       <4                                                  Ducting Floor    <1200    140                                                 Ducting Floor    <1200    220                                                 ______________________________________                                    

At test Feb. 25, 1997 it was found that the solid compositions haddiffused slowly and were greater than 80% intact. Following sampling,two further 15% v/v tea tree oil solid compositions were installed.These compositions had a gel type as described in Example 2 and allowedfor greater diffusion rate to compensate for the limited air flow in thesystem.

The results on Mar. 4, 1997 confirm positively this course of actionwith a reduction in CFUs from <1200 to 140 and 220.

The trials generally indicated a highly contaminated ducting environmentand continued as follows.

    ______________________________________                                        ACCESS POINT 1                                                                             11/03/97   18/03/97 25/03/97                                     ______________________________________                                        Hatch Door   <4         4        <4                                           Hatch Door   <4         <4       <4                                           Ducting Floor                                                                              380        120      220                                          Ducting Floor                                                                              570        1200     84                                           ______________________________________                                    

After Mar. 11, 1997 no further solid compositions were installed. Theair flow was very poor during week of Mar. 18, 1997. At Mar. 25, 1997the compositions had diffused by about 95%.

These tests confirm that the air conditioning fan system is preferablyrunning fully for each 24 hour period to fully maximise the solidcomposition potential. The refrigeration may be employed only for thecommercial times required by the operator--in this instance 9-13 hoursdaily. Running the fans is a low energy cost. The general benefits ofmoving large air mass around public facilities irrespective of tea treeoil gel solid composition disinfection are considerable.

Species of micro-organisms were identified during these trials. Noconclusive evidence was obtained to indicate the tea tree oildisinfection process is more specific for the elimination of anyparticular type.

The most dominant species present was Cladosporium herbarium, withPenicillium species the next most dominant. Aspergillus and Candida werealso observed. It was noted that the Aspergillus only appeared afterhuman intervention with the installation of a new inspection hatch atone ducting site.

TEST SITE B--TERRACE BISTRO

ACCESS POINT 4

Adjacent to a Window in the public bistro area. This area is some 70metres from the insertion point of the Tea Tree Oil Solid Compositionsin the ducting. For four weeks in the trial sampling was conducted asshown below:

    ______________________________________                                               CFU/cm                                                                        04/02/97                                                                              11/02/97  18/02/97  25/02/97                                   ______________________________________                                        Duct Wall-Side                                                                         >1200     >1200     >1200   >1200                                    Duct Wall-Rear                                                                         >1200     >1200     >1200   >1200                                    ______________________________________                                    

On the Mar. 4, 1997, one solid composition of the present invention wasinstalled. The count was more fully enumerated following thisinstallation.

    ______________________________________                                               04/03/97                                                                              11/03/97  18/03/97  25/03/97                                   ______________________________________                                        Duct Wall-Side                                                                         12000     2700      18400** 2600                                     Duct Wall-Rear                                                                         6800      2100      1900    1400                                     ______________________________________                                         **This anomalous result may be due in part to the reduction in air flow       that week. No further compositions were placed in this area after             04/03/97. It is noted that the extremely high counts at this point were       effectively reduced over 4 weeks by the insertion only of one 2.2 kilogra     tea tree oil solid composition. The significant reduction within one week     of these trails  04/03/97 to 11/03/97 indicate that in an area of high  #     infection such as this, solid compositions can be applied at more regular     intervals, or in greater mass per composition.                           

Test Conclusions

Air flow is preferably continuous. Fans can be left running at low cost.Refrigeration can be employed as required. High relative humidity valuesare conducive to formation of surface yeast and moulds constant air flowreduces this risk. Tea tree gel discs are preferably moderate releasetype. Optimum tea tree level found to be 15% v/v. Split air flowducting--generally considered outdated--must be clearly identified andcycles shown so that tea tree oil disc insertion points can be clearlydetermined. Tea tree oil gel disc are clearly effective in theelimination of fungus, moulds and yeasts and the maintenance of lowbacteria counts in commercial air conditioning ducting.

These examples demonstrate that the Tea Tree Oil Solid Composition ofthe present invention is highly effective and safe air conditioningducting system sanitiser. The composition is particularly effectiveagainst high mould, fungus and yeast microorganism numbers. The presenceof such high levels of micro-organisms is now recognised as posing aserious health risk to the buildings occupants.

The composition is particularly effective in well controlledrefrigerated air conditioning systems which run continuously. Theconstant air flow in such systems allows for even diffusion rates of thesolid composition tea tree oil gel discs.

The composition was found to be effective in commercial systems whichoperated fully for only limited times during any 24 hour period. Thetrials demonstrated a low cost way for such facilities to furtherimprove the general air quality of their systems. By limiting thegeneration of refrigerated air to the times selected and at other timesrunning the fans only, the solid composition worked more effectively andthe overall air quality improved.

In badly infected systems, the solid composition can return the systemto normal and accepted base line values for resident fungalmicroorganisms. By thereafter employing regular placement of the solidcomposition in air conditioning facilities these levels are economicallyand efficiently maintained.

It will be appreciated by persons skilled in the art that numerousvariations and/or modifications may be made to the invention as shown inthe specific embodiments without departing from the spirit or scope ofthe invention as broadly described. The present embodiments are,therefore, to be considered in all respects as illustrative and notrestrictive.

What is claimed is:
 1. A solid composition including a gum material andtea tree oil wherein the solid composition releases vapour containingthe tea tree oil when exposed to an effective flow of gas.
 2. A solidcomposition according to claim 1 wherein the gum material is acarrageenan.
 3. A solid composition according to claim 2 wherein thecarrageenan includes a kappa, iota or lambda fraction or a mixture ofone or more of the fractions.
 4. A solid composition according to claim1 wherein the gum material includes a galactomannan.
 5. A solidcomposition according to claim 4 wherein the galactomannan has amolecular weight of approximately 300,000.
 6. A solid compositionaccording to claim 4 wherein the galactomannan is derived from thelegume Ceratonia siliqua.
 7. A solid composition according to claim 4wherein the galactomannan is locust bean gum.
 8. A solid compositionaccording to claim 1 wherein the gum material includes a microbialexudate.
 9. A solid composition according to claim 8 wherein themicrobial exudate is Xanthan gum.
 10. A solid composition according toclaim 1 wherein the gum material includes a mixture of two or morecomponents selected from the group consisting of a carageenan, locustbean gum and Xanthan gum.
 11. A solid composition according to claim 1wherein the gum material is present in the solid composition at aconcentration of between 2 and 10 wt %.
 12. A solid compositionaccording to claim 11 wherein the gum material is present in the solidcomposition at a concentration of between 3 and 6 wt %.
 13. A solidcomposition according to claim 1 which further includes an aromatic oil.14. A solid composition according to claim 13 wherein the aromatic oilis selected from at least one of the group consisting of heliotropin,lavender, camomile, a lemon scented oil, the oil of Leptospermumliversidgeii, sandalwood and jasmine.
 15. A solid composition accordingto claim 14 wherein the aromatic oil is sandalwood.
 16. A solidcomposition according to claim 13 which further includes a fixative. 17.A solid composition according to claim 16 wherein the fixative isselected from the group consisting of musk ketone, coumerin, eugenol andvanillin.
 18. A solid composition according to claim 17 wherein thefixative is eugenol.
 19. A solid composition according to claim 1wherein the natural oil is solubilised by admixture with a non-ionicsurfactant.
 20. A solid composition according to claim 19 wherein thesurfactant is an alcohol ethoxylate.
 21. A solid composition accordingto claim 20 wherein the alcohol ethoxylate is polyoxtethylene(2)oleylether.
 22. A solid composition according to claim 1 wherein the solidcomposition is in the shape of a flat discus with a base surface and atop surface and a side wall connecting the base surface to the topsurface.
 23. A solid composition according to claim 22 wherein thediameter of the top surface is less than the diameter of the basesurface.
 24. A solid composition according to claim 22 wherein the ratioof the height of the side wall to the width of the top surface isbetween 1:10 and 1:11.5.
 25. A solid composition according to claim 22wherein the side wall is shaped in a camber.
 26. A solid compositionaccording to claim 22 wherein the angle of connection between the baseand top surfaces is equal to or less than 65 degrees.
 27. A solidcomposition according to claim 1 wherein the solid composition has atotal weight of between 0.5 and 5 kg.
 28. A solid composition accordingto claim 27 wherein the solid composition has a total weight of between0.9 and 3 kg.
 29. A method of preparing a solid composition according toclaim 1 which method includes:i) dissolving a gum material in an aqueoussolution; ii) heating the gum material solution to a temperature ofbetween 60° C. and 95° C.; iii) admixing the heated gum materialsolution with tea tree oil solution; and iv) placing the admixedsolution from step iii) into a mould.
 30. A method according to claim 29wherein the tea tree oil solution is in admixture with a non-ionicsurfactant.
 31. A method according to claim 30 wherein the non-ionicsurfactant is an alcohol ethoxylate.
 32. A method according to claim 31wherein the alcohol ethoxylate is polyoxyethylene (2) oleyl ether.
 33. Amethod of diffusing tea tree oil into the atmosphere which methodincludes exposing a solid composition including a gum material and teatree oil to an air flow such that the solid composition releases vapourcontaining the tea tree oil.
 34. A method according to claim 33 whereinthe solid composition further includes an aromatic oil.
 35. A methodaccording to claim 33 wherein the solid composition is exposed to an airflow by placing the solid composition in an air conditioning duct.
 36. Amethod of disinfecting an air conditioning system which method includesplacing a solid composition in a duct of the air conditioning system,the solid composition including a gum material and tea tree oil, whereinthe composition releases antimicrobial vapour containing the tea treeoil when exposed to an effective flow of gas.
 37. A method according toclaim 36 wherein the solid composition further includes an aromatic oil.